Copper extraction

3.3.3 Electrolysis

4.1.1 Crude oil

Copper extraction

  1. Traditional methods

    1. Copper is usually sourced from copper-rich ores in two main methods
    2. Copper can be smelted in a furnace by heating it with air to produce crude copper metal; for example, chalcocite is an ore of copper (I) sulfide, which reacts with oxygen to extract the copper: Cu2S(s) + O2 (g) → 2Cu(s) + SO2 (g)
    3. Copper ore can also be reacted with sulfuric acid to produce copper sulfate solution
    4. The copper from both methods can then be extracted & purified by electrolysis
    5. Here, the impure copper is the anode and a sample of pure copper is the cathode, with a copper salt solution, in this case copper (II) sulfate
    6. The ions present in the copper sulfate solution are: Cu2+(aq), SO2-4 (aq), H+(aq) & OH-(aq)
    7. The copper & hydrogen ions are attracted to the cathode where the copper is preferentially reduced: Cu2+(aq) + 2e- → Cu(s)
    8. The sulfate & hydroxide ions are attracted to the anode where the hydroxide ions are preferentially oxidised: 4OH-(aq) → 2H2O(l) + O2 (g) + 4e-
    9. The remaining hydrogen & sulfate ions react to form sulfuric acid solution: 2H+(aq) + SO2-4 (aq) → 2H2SO4 (aq)
    10. Copper atoms are also oxidised at the anode: Cu(s) → Cu2+(aq) + 2e-, and attracted to and reduced at the cathode: Cu2+(aq) + 2e- → Cu(s)
    11. The impurities drop off the anode and the cathode grows as copper atoms are transferred from the anode to the cathode, causing a mass & volume change in both electrodes

  2. New ways

    1. The supply of copper-rich ores is limited and being depleted so new ways of extracting copper from low-grade ore are being researched to limit the environmental impact of traditional mining
    2. Copper can be extracted by phytomining or bioleaching before being purified by electrolysis
    3. Phytomining uses plants to absorb metal compounds from the soil and are burned to leave ash that contains the metal compound1
    4. Bioleaching uses bacteria to produce leachate solutions that contain metal compounds2

  3. Electrolysis

    1. Copper can be extracted from solutions of copper salts by electrolysis

  4. Displacement

    1. Copper can be extracted from solutions of copper salts by displacement using scrap iron, such as copper (II) sulfate with iron: CuSO4 (aq) + Fe(s) → Cu(s) + FeSO4 (aq), wherein the ionic equation is Cu2+(aq) + Fe(s) → Cu(s) + Fe2+(aq)
    2. Copper is reduced since it gains electrons and is deionised
    3. Iron is oxidised since it loses electrons and is ionised
  1. Assessment of phytomining:
    Advantages: environmentally friendly
    Disadvantages: relatively slow ↩
  2. Assessment of bioleaching:
    Advantages: simpler so cheaper to operate; more environmentally friendly; bacteria are easily cultivated & recycled; can extract from ores that are too impure for other methods
    Disadvantages: relatively slow; toxic chemical are sometimes produced, such as sulfuric acid and H+ ions, which cause environmental damage ↩